The WoKaS-Iso Database: Workflow for a Global Compilation of Oxygen-18 and Deuterium Records in Karst Springs and Cave Drip Water for Enhanced Understanding of Karst Systems

Abstract

For analysing karst hydrogeological systems, observations of karst springs and cave drip water are considered indispensable. In addition to hydrometric observations, knowledge of oxygen and hydrogen stable isotope ratios has improved the understanding of vadose-zone and aquifer dynamics, while supporting system characterisation and modelling. However, the limited accessibility and high costs of stable isotope analyses in karst aquifers have hindered progress in karst research and impeded an accurate understanding of karst processes, particularly in comparative and large-scale studies. In this study, we present the workflow used to compile the WoKaS-Iso database, the first extensive collection of time-series data for oxygen-18 and deuterium isotopes in karst springs and cave drip water. The data were obtained from diverse sources, including publications, theses, reports, online archives, and collaborative initiatives worldwide. The database incorporates data from 241 springs and 74 caves, of which 73 caves contain records from 365 individual drip sites, while one cave contains input data only. In total, the database comprises 1,007 time series, including 389 spring time series and 618 cave drip-water time series. The compiled isotope records span the period from 1967 to 2024, with the strongest temporal coverage during the 2010s and continued coverage into the early 2020s. Of the included sites, 148 springs and 64 caves contain both δ¹⁸O and δ²H records, whereas 93 springs and nine caves contain only one isotope tracer. The datasets cover major karst regions worldwide, including China, the USA, Europe, the Middle East, and Australia. Of the included datasets, 79% of the spring datasets and 68% of the cave drip-water datasets have sampling intervals shorter than one month. By integrating isotopic records with ancillary environmental variables, including spring discharge, cave drip rate, precipitation, and rainwater isotope composition, the database provides a more comprehensive perspective on hydrological behaviour in karst aquifers, thereby advancing hydrogeological characterisation and modelling. The WoKaS-Iso database not only deepens the understanding of these complex systems but also supports sustainable water-resource management and has the potential to foster collaborative research.